Contributions of available substrates and activities of trophic microbial community to methanogenesis in vegetative and reproductive rice rhizospheric soil

Abstract: Potential of methane production and trophic microbial activities at rhizospheric soil during rice cv. Supanburi 1 cultivation were determined by laboratory anaerobic diluents vials. The methane production was higher from rhizospheric than non-rhizospheric soil, with the noticeable peaks during reproductive phase (RP) than vegetative phase (VP). Glucose, ethanol and acetate were the dominant available substrates found in rhizospheric soil during methane production at both phases. The predominance activities of trophic microbial consortium in methanogenesis, namely fermentative bacteria (FB), acetogenic bacteria (AGB), acetate utilizing bacteria (AB) and acetoclastic methanogens (AM) were also determined. At RP, these microbial groups were enhanced in the higher of methane production than VP. This correlates with our finding that methane production was greater at the rhizospheric soil with the noticeable peaks during RP (1,150 ± 60 nmol g dw ) with its high activity at RP, compared to the less activity with AM number at VP (9.8x10 2 cell g dw -1 ). Levels of AM are low in the total microbial population, being less than 1% of AB. These evidences revealed that the microbial consortium of these two phases were different

Subcellular proteomic characterization of the high-temperature stress response of the cyanobacterium Spirulina platensis

The present study examined the changes in protein expression in Spirulina platensis upon exposure to high temperature, with the changes in expression analyzed at the subcellular level. In addition, the transcriptional expression level of some differentially expressed proteins, the expression pattern clustering, and the protein-protein interaction network were analyzed. The results obtained from differential expression analysis revealed up-regulation of proteins involved in two-component response systems, DNA damage and repair systems, molecular chaperones, known stress-related proteins, and proteins involved in other biological processes, such as capsule formation and unsaturated fatty acid biosynthesis. The clustering of all differentially expressed proteins in the three cellular compartments showed: (i) the majority of the proteins in all fractions were sustained tolerance proteins, suggesting the roles of these proteins in the tolerance to high temperature stress, (ii) the level of resistance proteins in the photosynthetic membrane was 2-fold higher than the level in two other fractions, correlating with the rapid inactivation of the photosynthetic system in response to high temperature. Subcellular communication among the three cellular compartments via protein-protein interactions was clearly shown by the PPI network analysis. Furthermore, this analysis also showed a connection between temperature stress and nitrogen and ammonia assimilation

Agricultural biotechnology and the poor : proceedings of an international conference, Washington, D.C., 21-22 October 1999. Thailand: biotechnology for farm products and agro-industries.

Article "Thailand: biotechnology for farm products and agro-industries"  from "Agricultural biotechnology and the poor : proceedings of an international conference, Washington, D.C., 21-22 October 1999"

Insect-Specific Polyketide Synthases (PKSs), Potential PKS-Nonribosomal Peptide Synthetase Hybrids, and Novel PKS Clades in Tropical Fungi▿ †

Polyketides draw much attention because of their potential use in pharmaceutical and biotechnological applications. This study identifies an abundant pool of polyketide synthase (PKS) genes from local isolates of tropical fungi found in Thailand in three different ecological niches: insect pathogens, marine inhabitants, and lichen mutualists. We detected 149 PKS genes from 48 fungi using PCR with PKS-specific degenerate primers. We identified and classified 283 additional PKS genes from 13 fungal genomes. Phylogenetic analysis of all these PKS sequences the comprising ketosynthase (KS) conserved region and the KS-acyltransferase interdomain region yielded results very similar to those for phylogenies of the KS domain and suggested a number of remarkable points. (i) Twelve PKS genes amplified from 12 different insect-pathogenic fungi form a tight cluster, although along with two PKS genes extracted from genomes of Aspergillus niger and Aspergillus terreus, in reducing clade III. Some of these insect-specific fungal PKSs are nearly identical. (ii) We identified 38 new PKS-nonribosomal peptide synthetase hybrid genes in reducing clade II. (iii) Four distinct clades were discovered with more than 75% bootstrap support. We propose to designate the novel clade D1 with 100% bootstrap support “reducing clade V.” The newly cloned PKS genes from these tropical fungi should provide useful and diverse genetic resources for future research on the characterization of polyketide compounds synthesized by these enzymes

Up-regulated expression of desaturase genes of Mucor rouxii in response to low temperature associates with pre-existing cellular fatty acid constituents.

Transcriptional response of desaturase genes to low temperature was investigated in the dimorphic fungus Mucor rouxii. The two morphological forms of M. rouxii, yeast-like and mycelial cells containing different fatty acid profiles were shifted from 30 to 10C. Both cultures exhibited significantly altered fatty acid composition, whose content in polyunsaturated fatty acids increased as consequence of the temperature shift and was accompanied by a reduction of C18:1D9 about 2 h after the temperature shift. These changes were particularly significant in phosphatidylcholine and phosphatidylethanolamine fractions. Moreover, the fatty acid profiles of monoacylglycerol and diacylglycerol were also modulated in response to the lower temperature of incubation. The changes of membrane lipids of M. rouxii were due to the cold-induced expression of D9-, D12- and D6-desaturase genes. Although the mRNA levels of the three desaturases were transiently induced by lowering the temperature, the pre-existing composition of fatty acid profiles of mycelial and yeast-like forms of M. rouxii may have lead to different expression profiles of desaturase genes that modified their membrane physical state under cold shock. While expression of D12-desaturase gene contributedmainly to cold acclimation of mycelia, D9-desaturase expression was the main transcript identified in the yeast-like culture after temperature shift